The effect of some pre‐treatments on proteolysis during the ensiling of herbage

Abstract

Two experiments were carried out to examine the nitrogenous changes occurring in herbage during harvesting and ensiling. In the first, ryegrassclover was wilted rapidly in the laboratory (6 h) and in the field under good (48 h) and poor (48 h and 144 h) weather conditions. Protein breakdown and ammonia formation were negligible in herbage wilted rapidly and it was only when the crop was exposed to a prolonged wilt in humid conditions that appreciable proteolysis occurred. In the second experiment ryegrass-clover was ensiled in laboratory silos after treatment with varying levels of formic and sulphuric acids. An additional treatment included herbage inoculated with a mixture of lactic acid bacteria and glucose. The silos were opened after 4 and 50 d and samples were analysed for protein-N, ammonia-N, water-soluble carbohydrates and organic acids. Tliere was a high negative correlation between level of addition of either acid and the degree of proteolysis and deamination. Even at the highest levels of formic acid (7 7 g per kg) and sulphuric acid (4 0 g per kg) additions, however, about 45 % ofthe original herbage protein was degraded after 50 d in the silo. The inoculum treatment was also effective in reducing proteolysis, the effect after 50 d being comparable with formic acid applied at a rate of 41 g per kg.

Protein degradation and ensiling characteristics of red clover and alfalfa wilted under varying levels of shade

“…From these results, it appears that the total extent of protein degradation in the silo is largely independent of the level of NPN in wilted herbage and may be related to substrate availability (McKersie 1985). Carpintero et al (1979) found that NPN was only slightly higher in wilted ryegrass-white clover mixtures if wilting in dry conditions was extended from 6 to 48 h, but was significantly higher (particularly NH 3 -N) if the mixtures were wilted for 48 or 144 h under moist conditions. They could not conclude that either the time to wilt or the wilting conditions affected silage NPN levels, however, because the wilted forage was not ensiled.…”

“…The level of NPN in wilted legume and grass herbage has been reported to increase with wilting time in several other studies (Carpintero et al [1979] for a ryegrass/white clover mixture; Anderson [1983] and Charmley and Thomas [1989] for perennial ryegrass; Muck [1987] for alfalfa) and this increase was a result of the action of plant proteinases. Unlike the current study, in which specific DM content of wilted forage was predetermined, the purpose of most of these experiments was to study the effect of DM content on silage characteristics or to evaluate the effect of wilting under less than ideal conditions.…”

“…Unlike the current study, in which specific DM content of wilted forage was predetermined, the purpose of most of these experiments was to study the effect of DM content on silage characteristics or to evaluate the effect of wilting under less than ideal conditions. In some cases the DM content of fresh and wilted herbage was not substantially different (Carpintero et al [1979] under moist wilting conditions; Anderson [1983] under poor wilting conditions), which may have resulted in a confounding of proteolysis with DM. There was a significant species × wilting-treatment interaction for NPN in wilted forage in 1993 (Table 3).…”

“…Ryegrass (type not stated by authors) wilted under moist conditions (72 h to reach 35% DM) contained more NPN than forage wilted under dry conditions (24 h to reach 43% DM) (Macpherson 1952). Carpintero et al (1979) reported higher levels of NPN in wilted ryegrass (Lolium multiflorum L. and Lolium perenne L.)/clover (Trifolium repens L.) mixtures when forage was wilted under poor conditions for 48 or 144 h. Macpherson (1952) and Carpintero et al (1979) speculated that the difference in NPN levels in wilted forage would carry over into the silo, but they did not ensile the wilted forage to test their hypothesis. Charmley and Thomas (1989) found that perennial ryegrass (L. perenne 'Melle') wilted for 43 h contained about 25% more NPN than herbage wilted for 19 h, but silage NPN levels were similar regardless of drying treatment.…”

The effect of cut, stage of growth and wilting on nitrogenous compounds and protein solubility in grass silages

“…Field wilting before ensiling, commonly practiced to improve silage quality, if done under adverse drying conditions, enhances the activity of plant enzymes and may negatively increase the proportion of NPN in herbage (Carpintero et al, 1979;Anderson, 1983;Gordon, 1989). It is generally assumed that silage NPN and soluble-protein N are rapidly utilized in the rumen (Thomas et al, 1985;Tamminga et al, 1991) and that the rapid release of ammonia can be one of the reasons for poor utilization of grass silage protein (Thomas et al, 1985).…”